Direct access storage devices (DASD) have become part of everyday life, and as such, expectations and demands continually increase for greater speed for manipulating and for holding larger amounts of data. To meet these demands for increased performance, the mechano-electrical assembly in a DASD device, specifically the Hard Disk Drive (HDD) has evolved to meet these demands.
Advances in magnetic recording heads as well as the disk media have allowed more data to be stored on a disk's recording surface. The ability of an HDD to access this data quickly is largely a function of the performance of the mechanical components of the HDD. Once this data is accessed, the ability of an HDD to read and write this data quickly is a primarily a function of the electrical components of the HDD.
FIG. 1 (Prior Art) shows HDD 100 with its cover removed to allow the internal components of HDD 100 to be visible. Actuator assembly 120 pivots about pivot bearing 145 and moves magnetic head 125 arcuately across disk surface 130 to record and retrieve data from concentric circles of data known as data tracks 135. To allow more data to be stored on disk surface 130, more data tracks must be stored more closely together.
The quantity of data tracks 135 recorded on disk surface 130 is determined partly by how well magnetic head 125 can be positioned and made stable over a desired data track 135. The quantity of data tracks 135 is a direct indicator of the amount of data stored in HDD 100. Vibration or unwanted relative motion between the magnetic head 125 and disk surface 130 will affect the quantity of data tracks 135 recorded on disk surface 130.
Although the mass, stiffness and geometry of the components in actuator assembly 120 directly affect the stable positioning of magnetic head 125, vibration energy that acts on actuator assembly 120 and disk surface 130 is also a major factor in the stable positioning of magnetic head 125. If excessive, vibration energy will impart oscillating motion to actuator assembly 120 and move magnetic head 125 from a desired position over data tracks 135.
There are many sources of vibration energy in an HDD, e.g. air from the disk impinging on actuator assembly 120, vibration from spindle motor 140, or external motion coming into HDD 100. Aside from these sources of vibration energy, actuator assembly 120 can cause itself to vibrate in an uncontrolled manner. While performing its function of moving magnetic head 125 arcuately across disk surface 130, the components and/or structure of actuator assembly 120 can begin to vibrate and prevent magnetic head 125 from arriving in a timely manner, or settle in, and following a desired data track 135.
In an effort to mitigate unwanted relative motion between the magnetic head 125 and disk surface 130, HDD manufacturers are beginning to configure HDDs with a secondary actuator in close proximity to magnetic head 125. A secondary actuator of this nature is generally referred to as a microactuator because it typically has a very small actuation stroke length, typically plus and minus 1 micron. A microactuator typically allows faster response to relative motion between magnetic head 125 and data track 135 as opposed to moving the entire structure of actuator assembly 120.
Micro actuator 150 makes it possible for a magnetic head 125 to settle in on a data track 135 while most of actuator assembly 120 and/or disk surface 130 could possibly be vibrating as a result of the actuation process or external vibration energy. An additional requirement of microactuator 150 is to provide a conveyance means for written and read data to be transferred from magnetic head 125 to outside HDD 100 via connector 117.
Microactuator 150 is part of the data transfer circuit that comprises in part: magnetic head 125, conductors on suspension 180, flex cable 110, and arm electronics (A/E) 115. All components of the data transfer circuit must be able to transfer data at a prerequisite data rate or frequency. HDD customers are demanding higher data rates to enable them to manipulate data faster. Today's data rate targets are in the range of 1-3 GHz (Giga-hertz). In this data rate range and above, the impedance of the data transfer circuit, sometimes referred to as a transmission line, becomes a concern for achieving these high data rates.
The problem for microactuator designers is to devise a conveyance means for written and read data that can convey high data rates from magnetic head 125 to suspension 180, while magnetic head 125 is moving relative to suspension 180.